The invention relates to a method and a device for measuring operational density and/or operational sound velocity in a gaseous medium.
In the sector of gas measurement technology, one constantly encounters the same measurement tasks. A characteristic variable of natural gas, which is very important, is density. However, determination of density is not trivial. Previous measurement methods are either expensive or require a lot of space.
Such a measurement method is described in German Patent No. DE 37 41 558 A1, in which a device for determining the resonance frequency of a vibrating organ fundamentally in the form of a Helmholtz resonator is described. The density and the flow velocity of a fluid are determined from the resonance frequency. In this connection, the vibrating organ is fundamentally disposed in a housing, in the form of a Helmholtz resonator, and chambers having the same volume are provided on both sides of the vibrating organ, through which chambers the fluid flows. In this connection, the vibration of the vibrating organ is influenced by the fluid, and thereby changes the vibration behavior of the vibrating organ, in measurable manner, as a function of the density of the fluid. However, only a single frequency is measured as the resonance frequency, and the measurement device is optimized in targeted manner, to simplify the underlying interpretation of the measurement values. In the case of such an arrangement, no determination of the sound velocity is possible, either, since the determined single frequency does not yield this. Furthermore, this is a self-exciting vibration circuit, the resonance frequency of which can only be determined for an impedance maximum.